Prior art systems which are capable of generating characters having video enhanced edges have been of both analog and digital types.
The analog devices have usually not functioned satisfactorily because they have been composed of analog delay lines and other components which are subject to drift and noise problems. In addition, such systems have not been capable of providing edge information on the entire periphery of the character and therefore have been unable to generate the complex video character and edge information required by modern-day display devices.
The digital prior art approaches which have been capable of providing the necessary edge information around the entire periphery of the character have had other problems in that they are generally complex and costly. In addition, with these systems it is often difficult to change basic character formats without a substantial redesign and rewiring of the circuitry and without increasing the number of integrated circuit devices used in the system for generating the edge information.
One prior art digital circuit capable of generating enhanced video edges is described in U.S. Pat. No. 3,918,039. However, this circuit uses a plurality of shift registers and a complex gating arrangement to generate the required information. It is therefore difficult to change the format of the basic character without a rewiring of the system.
Another similar digital edge enhancement circuit is shown in U.S. Pat. No. 4,186,393. This circuit uses a simplified gate arrangement to generate the edge information, but still utilizes a group of shift registers to delay the incoming video information for the generation of appropriate information. Therefore, a change in the basic character format, such as an increase in the width of the character requires an increased number of shift registers.
It is therefore an object of the present invention to provide a simplied, all digital video character enchancement system.
An additional object of the invention is the generation of video character information having all-around edge information.
A further object of the invention is the generation of video character and edge information utilizing simplified, generator circuitry which does not require an increase in the number of shift registers if the basic character format is changed.